Looking Up: Venus closes in on Mars in pre-dawn sky

Friday

Sep 29, 2017 at 1:01 PMSep 29, 2017 at 1:01 PM

By Peter Becker More Content Now

Early bird alert: About 45 minutes before sunrise this week (around 5:30 a.m.), be sure to take a look low in the eastern sky for brilliant white Venus, very close to the much diminished but ruddy planet Mars.

With a nice, clear pre-dawn sky, Venus is easy to see, glowing at magnitude -3.9. It is typically called the ďMorning StarĒ when on this side of the Sun, rising before the Sun and announcing to the world waiting for a new day, by its reflected sunlight that day is on schedule once more.

Of course you could already sense that with the brightening in the east; solar rays refracting high in the upper atmosphere herald the Sunís soon arrival.†

The second planetís eternal shroud, hiding its surface from our telescopic gaze, serves as an excellent reflector of the Sun, so much brighter than we ever have in our more distant orbital path.

Mars, however, is further out from the Sun than we ever attain. The Fourth Planetís remoteness is all the more extreme from this perspective, from our line of sight crossing the orbit of Venus and well beyond in the glow of the Sun.

When Mars is at its closest approach to Earth, which happens about once in in two years, it can gleam at magnitude -2.9, like a gloriously bright red-orange star. Currently, Mars is magnitude +1.8.†

If you saw Mars this dim in a dark sky, it would be easy to see as any of the brighter stars of the Big Dipper.

Since Mars is situated relatively close to the Sun from our line of sight, it is much harder to see due to the glare of dawn. Thatís why you should use binoculars to pick out Mars, shining near the much brighter planet Venus.

Venus appears just above Mars at this time, in the last week of September and first few days of October. Venus is dipping down, and appears closest to Mars on October 5.

Venus will seem to be nearly touching Mars, with unaided eyes; at the closest, they will appear only about a fifth of one degree apart. For comparison, the apparent width of the Full Moon is about one-half degree.†

About the magnitude scale: The lower the number, the brighter is the star or planet. Each magnitude is approximately 2.5 times brighter or dimmer than the next. The faintest star you can see with the unaided eyes under very good conditions is typically +6. The brightest star in the night sky, Sirius, is magnitude (minus) -1.4 (look for Sirius in the pre-dawn sky, in the south-southeast). Vega, which shines high in the evening sky at this time of year as darkness falls, is magnitude 0.0. The Sun is -27.

The Full Moon, on October 5th, will be magnitude -12.

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Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at news@neagle.com. Please mention in what newspaper or web site you read this column.

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